This invention relates to automatic vehicle identification systems and particularly to such systems which include the ability to accurately modify data stored in a vehicle transponder while the vehicle is in motion.
There is a need for an identification system wherein moving objects such as railroad cars and motor vehicles, passing an interrogation station, identify themselves for both accounting and control purposes. Such a system would also be applicable to boats, trucks, shipping containers, mail bags, pallets, etc. In addition to the above uses the ability to read, write, delete or modify data in a digital form makes the system applicable to a variety of uses, an example of which is a credit card. In this case, the system serves as a portable interrogable memory for information such as a credit balance.
The complexity of modern transportation systems has increased to the point where automated traffic management has become essential for efficient operation. This is true of railways, highway truck transportation, and urban transit systems. Early attempts to meet these needs followed the premise that all that was necessary was to identify the individual vehicles automatically and all other management functions could then be carried out in a central computer. This notion belies the fact that a vast amount of data communications with a central data base are then required. In many cases, particularly when operations cover a large geographic area, this approach is both expensive and impractical. In addition, initial encoding of earlier devices was not satisfactory. The device was either factory-programmed, requiring a cross-reference table to relate the arbitrary number to that of the vehicle, or it was field-programmed by physical and/or electric contact, requiring sealing in the field to ensure package integrity.
An alternative to the centralized storage of vehicle data is to store data in the vehicle itself. This requires a system which includes data storage in the vehicle and the ability to change that information. Such systems are disclosed, for example in Baldwin, et al., U.S. Pat. No. 4,870,419 and Cardullo, et al., U.S. Pat. No. 3,713,148. Although these known systems are capable of changing data stored in a moving vehicle, both transmit signals specifying data change, then do nothing to assure that accurate data change actually occurs. Data modification without assured accuracy can result in many vehicles containing inaccurate data to the detriment of both the operators of those vehicles and the traffic control and regulation systems relying on such data.
A need exists for an automatic vehicle identification system having the ability to change the content of memory of a moving vehicle and which provides assurances that such changes are accurately completed.
Also needed is a reader-transponder system which utilizes a multi-function transponder. More specifically a multi-function transponder can cooperate with a reader or an interrogator to perform the following functions with the vehicle in motion:
1) Transmit vehicle identification and other basic data;
2) Accept programming of input data from the interrogator;
3) Communicate with other equipment on board of the vehicle such as a visual display, speed alarm and road advisories; and
4) Work with additional input from the vehicle such as weight on the road as measured by a vehicle road sensor such as disclosed and claimed in C. M. Tromp U.S. Pat. No. 4,799,381 ("Vehicle Road Sensor").